Conventional solar heating systems must collect high grade solar heat (defined herein as heat which raises the temperature of a collection medium substantially above the desired temperature for the living space), which is only possible during a short part of even a sunny day. When it is cloudy, or when the sun is low in the sky, the heat collected is low grade heat which cannot be used directly to heat a living space.
Most conventional collectors employ a liquid collection medium such as water or another liquid. Such a system requires comprehensive plumbing on or in the roof of a house. During the night, when no solar collection is possible, the liquid in the exposed plumbing can freeze and burst the pipes. Alternatively, an exotic and less desirable heat collection medium must be provided, or the system must be drained whenever freezing is possible.
When air has been used as the collection medium, heat collection has been much less efficient, for in prior systems a large volume of air laden with low-grade heat has been circulated through the heat reservoir to store heat.
Still another problem in solar heating has been to provide simultaneous collection and utilization of heat. Optimum solar collection is often achieved on clear days which are also quite cold, so heat must then be collected rapidly at the same time heat is being withdrawn rapidly from the reservoir to heat the living space. A optimized solar collection and heating system must thus be able to collect heat and to transmit heat to the living space simultaneously, which is not achieved in many systems, or is achieved only by providing auxiliary heat sources.
Furthermore, the art has not provided a solar heating system adapted to supply usable heat from the sun under a wide variety of operating conditions, such as during cloudy days or sunny days and during the day or night.
Finally, the prior art has not provided adequate control mechanisms to allow heat pumps to be employed over a wide variation in operating conditions, to allow solar heat to be extracted and used in a living space when operating conditions are extreme without damaging or inefficiently operating the heat pumps.